In recent years, communication technology has widely spread in terms of number of users and amount of use of the telecommunication services by the users. This also led to an increase in the number of different technologies and technological concepts in use.
Thereby, developments have been especially remarkable in mobile communication networks. In this connection, one trend is an increasing usage of communication protocols for wireless communications, that have originally been designed and hitherto been used for fixed networks. The most popular and widely spread example is the Internet Protocol (IP) suite. The IP protocol will for example be utilized in Third Generation (3G) mobile communication networks such as the Universal Mobile Telecommunication System UMTS.
However, when using such fixed network protocols and/or technologies for mobile communications, there may occur a plurality of problems because of these protocols and/or technologies not being specifically designed for the conditions and needs of mobile communications.
In the following, there is explained an example situation for illustrating such a non-conformance.
In an IP-based (fixed) network, hosts, i.e. communication entities such as terminals, listen to IP level (network layer) control messages in order to obtain network configuration information and/or perform self-configuration for IP addressing based on system information. These IP level (network layer) control messages can be unicast to a single host or can be multicast or broadcast to multiple or all (in case of broadcast) hosts within the network. One typical example of such IP level control messages is an IPv6 Router Advertisement, wherein IPv6 stands for version 6 of the Internet Protocol.
Nevertheless, the applicability of the present invention to be described below is not limited to IPv6. Also, IPv4 or any other version of IP or even any other packet-based protocol type—whether presently known or being developed in the future—may be used in connection with the present invention.
Routers in the network advertise their presence or existence together with various link and router parameters. Router Advertisements (RAs) contain prefixes that are used for on-link determination and/or address configuration, a suggested hop limit value, etc. Further, Router Advertisements (and prefix flags) allow routers to inform hosts how to perform address auto-configuration. For example, some routers specify whether hosts should use stateful (e.g. Dynamic Host Configuration Protocol version 6; DHCPv6) and/or autonomous (stateless) address configuration.
Routers usually send such Router Advertisements in two ways, i.e. either periodically multicast unsoliciated RAs, or unicast RAs to the soliciting host in response to a soliciting message such as a Router Solicitation message.
Therefore, the triggering for a router to send the Router Advertisement is either an expiration of a respective RA timer (for multicast RAs) or a reception of a Router Solicitation message (for unicast RAs). Both of these events are events of the IP or network layer according to the ISO/OSI (International Standards Organization/Open System Interconnection) specification.
The existing prior art (network or IP layer) approaches as described above are originally designed and have been experienced to be well suitable for fixed networks. However, they are hardly applicable to a system like a wireless network where seamless mobility is vital, handovers occur very often, and maintaining a high spectrum efficiency is also essential. The issues and problems in this regard are listed in the sequel.
In a wireless network, when a terminal such as a mobile node MN or a mobile station MS attaches to a new system (i.e. when MN is powered up or performs a handover to an area covered by a different access router), it first sets up a link level (L2) connection and obtains a link level identity. Then, the MN needs to obtain a Router Advertisement on the basis of which its IP address can be configured. As mentioned above, the Router Advertisement is a network layer (L3) event. Therefore, according to the ISO/OSI specification, normally a logical link layer connection has to be set up before communication and/or signaling on the network layer is possible. Thereafter, if the periodic (multicast) Router Advertisement RA is sent shortly before (in relation to the timer period), the terminal may need to wait until the next periodic Router Advertisement RA is sent. Alternatively, the terminal may choose to send a request message such as a Router Solicitation message to explicitly request for a Router Advertisement. After receiving the Router Solicitation message, the respective access router AR may nevertheless decide to delay the response in case the next periodic RA is already scheduled to occur within short. This basically indicates that the mobile terminal may experience a rather long and possibly unacceptable (in particular, for certain realtime services) delay before it can request and/or configure its IP address after attaching to a wireless system.
Even if the regular prior art procedure described above may be applicable to the terminal power-up procedure where a longer delay is still tolerable (e.g. for non-realtime services), it is not applicable to handover procedures where a seamless communication has to be ensured. Moreover, it is still beneficial if such a delay can be minimized to the lowest value even in situations being tolerable to longer delays. In addition, reducing such delay during an inter-AR handover, i.e. during a handover where a terminal hands over to another access router, will reduce the overhead due to tunneling between the old access router and the new access router for the terminal performing the handover.
In the above procedure, the IP level control message such as the Router Advertisement is triggered by an event in the IP level. For example, the Router Advertisement is sent either upon expiry of the respective RA timer or upon reception of a request such as a Router Solicitation message.
However, the presented procedures have several disadvantages in terms of excessively long delays until network layer configuration is established, low spectrum efficiency due to excessive network layer signaling, and inflexibility. For example, with the known solutions, whenever a new terminal attaches to the network (i.e. to the base transceiver station), a Router Advertisement is to be sent, even if this is not necessary.
Therefore, improving network layer, and in particular IP layer handover and power up performance has been identified as an important objective for further development. For this purpose, a solution to the above problems and drawbacks is needed.